1. Field of the Invention
The present invention relates to a sheet molding compound which is useful for the production of fiber-reinforced plastic molded articles by the compression molding process or the like, and to a process for preparing the same.
According to the sheet molding compound of the present invention, the resin compound exhibits good flowability during the step of molding, and the reinforcing fiber uniformly flows in the same direction along the plane of the sheet. Therefore, the fiber-reinforced plastic molded articles prepared by using the sheet molding compound of the present invention contain the reinforcing fibers at a uniform density to exhibit uniform strength, and exhibit very good appearance without permitting the reinforcing fiber to protrude on the surfaces of the molded articles.
Accordingly, the sheet molding compound of the present invention can be effectively used for producing fiber-reinforced plastic molded products such as fishing reels, electronics apparatus container, bracket, brake cover, gears and automobile parts, which require precision, uniform strength and good appearance.
2. Description of the Prior Art
A variety of molded products which had hitherto been made of metals, such as bath tubs, water tanks, automobile parts and the like, have now been made of a resin compound consisting of reinforcing fibers such as cut fibers or glass fibers and matrix resins, and it is considered that this tendency will further grow in the future. Fiber-reinforced plastic molded products are produced by the cast molding process, transfer molding process, matched-die molding process, and compression molding process. The resin compounds must exhibit good flowability during the molding by the above-mentioned processes and, therefore, are not allowed to contain reinforcing fibers in large amounts, from which it is difficult to produce molded products having increased strength. Particularly, the molded products have markedly decreased density of reinforcing fibers at the corner portions which accounts for the reduced strength at the corner portions as compared with other portions. Further, the reinforcing cut fibers in the resin compound undergo the three-dimensional flow during the step of molding; cut fibers float on the surfaces of the fiber-reinforced plastic molded products made of the resin compound to deteriorate the appearance. In the conventional art, therefore, it was necessary to beautifully finish the surfaces of the molded products.
The U.S. Pat. No. 4,141,929 discloses a new dry, hardenable, thickened, resinous sheet molding composition containing axially aligned continuous filaments, which can be molded by the matched-die molding process. This sheet molding compound contains unidirectionally aligned reinforcing fibers and is effective for producing fiber-reinforced plastic molded products of elongated shapes such as fishing rods and pole vault poles, but is not suited for producing fiber-reinforced plastic molded products having very complicated shapes such as spinning reels, electronics apparatus container, bracket, brake cover, or gears.